Magnetic optical member with a polymer substrate

ABSTRACT

This invention provides a magnetic optical member that can obtain a large magneto-optical effect using a rare-earth iron-garnet-based material and a method of producing the same.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a magnetic optical member used in anoptical isolator and an optical magnetic recording medium and the like,and to a method of producing the same.

2. Description of the Related Art

An optical isolator used in optical fiber communication systemsgenerally includes, for example, a pair of polarizers and a Faradayrotator interposed between the pair of polarizers. The Faraday rotatorhas the Faraday effect (magneto-optical effect) and rotates a polarizingsurface of incident light by 45 degrees, that is the Faraday rotationalangle is set to 45 degrees.

Recently, in addition to the optical isolator, an optical deviceutilizing the above-mentioned magneto-optical effect (hereinafterreferred to as magnetic optical member), such as an optical magneticrecording medium (an optical magnetic disk) and an optical switch hasbeen greatly used.

In recording of optical magnetic recording using, for example, anoptical magnetic recording medium (an optical magnetic disk),temperature of the optical magnetic recording medium is locallyincreased by irradiation with laser light and recording is made with anexternal magnetic field only in the local portion where coercive forcewas decreased by the temperature increase. Since the spot diameter ofthe laser light can be reduced to about its wavelength, that is, asubmicron length or so by narrowing the light with a lens, high densityrecording can be performed when combined with a vertically magnetizedfilm as a recording medium.

The reproduction of information recorded on the optical magneticrecording medium utilizes the principle (Kerr effect) that when anoptical magnetic recording medium is irradiated with linearly polarizedlaser light, rotation is made in mutually opposite directions dependingon the direction of the polarizing surface to the reflected light, thatis, depending on whether the direction is upward or downward withrespect to the vertical direction to the film surface. On the opticalmagnetic recording medium (an optical magnetic disk), a laser lightguiding groove is formed into a spiral shape so that minute recordingbits can be correctly recorded and reproduced. The reproducing device(optical magnetic disk drive) is provided with an automatic focusingmechanism and an automatic tracking mechanism for tracking the laserlight along the groove in the optical system (pick-up head).

Further, recently high densification has been required for the opticalmagnetic recording medium, and development of a blue color laser fornarrowing the laser light has been attempted. In this case, an opticalmagnetic recording medium (magnetic optical member) having a large Kerrrotational angle for short wavelength laser light is required. Sincerare earth iron garnet based materials, for example, bismuth-substitutedrare earth iron-garnet (BiYIG) and the like have a large Kerr rotation(magneto-optical effect) at the short wavelength, even if the recordingspot diameter, that is, the recording area is reduced, a large signalcan be obtained. Thus, to form a magnetic optical member using BiYIGwith a large magneto-optical effect is considered.

Incidentally, the crystal structure of the BiYIG is amorphous just afterthe film formation, and annealing treatment to enhance crystallinity at600° C. or more is needed for obtaining large Hc (and excellent magneticoptical characteristics). On the other hand, the optical magneticrecording medium is generally placed on a resin substrate, which isdeformed by the above-mentioned heat treatment. Therefore, under theabove circumstances, it is difficult to form the optical magneticrecording medium using a rare earth iron garnet based magnetic material,and an excellent magneto-optical effect that the rare earth iron garnetbased material possesses cannot be utilized.

Incidentally, it is thinkable that glass is used as the substrate.However, a glass substrate is difficult to form a guiding groove forlaser light. Therefore, the use of the glass was not effective as thesolution of the above-mentioned problems.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above-mentionedcircumstances and, therefore, an object of the present invention is toprovide a magnetic optical member that can obtain a largemagneto-optical effect using a rare earth iron garnet based material,and a method of producing the same.

According to a first aspect of the present invention, a magnetic opticalmember is characterized by comprising a polymeric substrate on which amagnetic optical thin film made of crystalline rare earth iron garnet isformed.

According to a second aspect of the present invention, the magneticoptical member in the first aspect of the present invention ischaracterized in that there are provided two dielectric multi-layerfilms in which plural kinds of dielectric materials having differentoptical characteristics are alternately laminated with regularity inthickness, and in that the magnetic optical thin film is placed betweenthe two dielectric multi-layer films.

According to a third aspect of the present invention, the magneticoptical member in the first or second aspect of the present invention ischaracterized in that the polymeric substrate is a thermoplastic resinsubstrate.

According to a fourth aspect of the present invention, the magneticoptical member in any one of the first to third aspects of the presentinvention is characterized in that the polymeric substrate is atape-shaped, film-shaped, or sheet-shaped substrate.

According to a fifth aspect of the present invention, the magneticoptical member in any one of the first to fourth aspects of the presentinvention is characterized in that the magnetic optical thin film iscapable of magnetic recording.

According to a sixth aspect of the present invention, a method ofproducing a magnetic optical member comprising: two dielectricmulti-layer films in which plural kinds of dielectric materials havingdifferent optical characteristics are alternately laminated withregularity in thickness; a magnetic optical thin film of rare earthiron-garnet, placed between the two dielectric multi-layers; and apolymeric substrate on which the layers and film are formed, ischaracterized in that the magnetic optical thin film is crystallizedwithout deforming the polymeric substrate by the pulse heating whereininfrared beam is intermittently irradiated.

According to a seventh aspect of the present invention, the method ofproducing a magnetic optical member in the sixth aspect of the presentinvention is characterized in that the magnetic optical thin film isheated without disordering the cyclic structure of the dielectricmulti-layer films.

According to an eighth aspect of the present invention, the method ofproducing a magnetic optical member in the sixth or seventh aspect ofthe present invention is characterized in that the polymeric substrateis cooled during heating the magnetic optical thin film.

According to a ninth aspect of the present invention, the method ofproducing a magnetic optical member in the sixth aspect of the presentinvention is characterized by using, in place of the infrared beam,laser light having a wavelength with which the light is not absorbed inthe polymeric substrate but is absorbed in the magnetic optical thinfilm.

According to a tenth aspect of the present invention, the method ofproducing a magnetic optical member in the ninth aspect of the presentinvention is characterized in that the laser light has a wavelength withwhich the light is not absorbed in the dielectric multi-layer film.

According to an eleventh aspect of the present invention, the method ofproducing a magnetic optical member in the tenth aspect of the presentinvention is characterized in that scanning with the laser light isperformed.

According to a twelfth aspect of the present invention, the method ofproducing a magnetic optical member in any one of the sixth to eleventhaspects of the present invention is characterized in that the polymericsubstrate is a thermoplastic resin substrate.

According to a thirteenth aspect of the present invention, the method ofproducing a magnetic optical member in any one of the sixth to twelfthaspects of the present invention is characterized in that the polymericsubstrate is a tape-shaped, film-shaped, or sheet-shaped substrate.

According to a fourteenth aspect of the present invention, the method ofproducing a magnetic optical member in any one of the sixth tothirteenth aspects of the present invention is characterized in that themagnetic optical thin film is capable of magnetic recording.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings.

FIG. 1 is a view showing an infrared ray introducing heater 220according to a first embodiment of the present invention;

FIG. 2 is a cross-sectional view showing a one dimensional magneticoptical crystal according to the first embodiment of the presentinvention;

FIG. 3 is a view showing a heat treatment pattern by the infrared rayintroducing heater of FIG. 1;

FIG. 4 is a view showing the X-ray diffraction pattern of the onedimensional magnetic optical crystal subjected to heat treatment forcrystallization;

FIG. 5 is a view showing the Faraday rotational angle of the onedimensional magnetic optical crystal subjected to heat treatment forcrystallization;

FIGS. 6A and 6B are views showing the transmissivity spectrum of adielectric multi-layer film before heating;

FIGS. 7A and 7B are views showing the transmissivity spectrum of thedielectric multi-layer film after heating;

FIG. 8 is a view showing the transmitted wavelength spectrum of the onedimensional magnetic optical crystal of FIG. 2;

FIG. 9 is a view showing the Faraday rotational angle of the onedimensional magnetic optical crystal of FIG. 2;

FIG. 10 is a view showing a laser heater according to a secondembodiment of the present invention; and

FIG. 11 is a view showing a characteristic of laser light used in thelaser heater of FIG. 10.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A description will be given in the following on a one dimensionalmagnetic optical crystal (magnetic optical member) according to a firstembodiment of the present invention and a method of producing the same,with reference to FIGS. 1 to 9.

In this first embodiment as shown in FIGS. 1 and 2, an indium sheet 202is set on a water-cooled substrate holder 201, a polymeric substrate 203is placed on the indium sheet 202, and a glassy carbon 204 as a lightcondensing plate is set on the polymeric substrate 203.

On the polymeric substrate 203 is laminated a (SiO₂/Ta₂O₅)^(n) layer 210(one of dielectric multi=layer films, n: the number of the laminatedlayers) in which a Ta₂O₅ film (dielectric material) and a SiO₂ film(dielectric material) having different optical characteristics arealternately laminated with regularity in thickness. The Ta₂O₅ film(dielectric material) and the SiO₂ film (dielectric material) aretransparent in the visible ray region and are formed with an oxidehaving high environmental stability.

The polymeric substrate 203 is made of a thermoplastic resin such asPMMA (polymethyl methacrylate) or PC (polycarbonate) or the like, andtakes a tape shape, a film shape, or a sheet shape.

Further, on this (SiO₂/Ta₂O₅)^(n) layer 210 is formed a bismuthsubstituted yttrium-iron-garnet thin film (BiYIG thin film) 207 (amagnetic optical thin film) which becomes capable of magnetic recordingby heat treatment described later. Then, the BiYIG thin film 207 in thisstate is subjected to heat treatment for crystallization with aninfrared ray introducing heater 220 as will be described later. Afterthat, on the (SiO₂/Ta₂O₅)^(n)/BiYIG including the crystallized BiYIGthin film 207 is formed a (Ta₂O₅/SiO₂)^(n) layer 211 (the other of thedielectric multi-layer films) to form a one dimensional magnetic opticalcrystal 200 (one dimensional photonic crystal) having a(SiO₂/Ta₂O₅)^(n)/BiYIG/(Ta₂O₅/SiO₂)^(n) structure shown in FIG. 2. Informing the one dimensional magnetic optical crystal 200 a sputteringdevice is used.

The infrared ray introducing heater 220 includes an infrared raygenerating portion 221 for generating an infrared beam, a glassy carbon204 for condensing the infrared beam, a cooling mechanism 222 forcooling the substrate holder 201, and a thermocouple 223 that is placedin contact with the surface of the glassy carbon 204 and is used as atemperature monitor during heating.

In the heat treatment for crystallization of the BiYIG thin film 207with the infrared ray introducing heater 220, the non-heat-resistingsubstrate 203 and the (SiO₂/Ta₂O₅)^(n) layer 210 are cooled through thesubstrate holder 201.

On the other hand, during the heat treatment only the BiYIG thin film207 is heated by the glassy carbon 204 whose temperature has beenincreased with infrared rays, to thereby crystallize the film and obtainexcellent magnetic characteristics. In this case, the infrared beam isintermittently emitted (pulse-heated).

In this first embodiment, the BiYIG thin film 207 is formed on the(SiO₂/Ta₂O₅)^(n) layer 210 and is subjected to heat treatment forcrystallization with infrared rays while cooling the polymeric substrate203 and the (SiO₂/Ta₂O₅)^(n) layer 210 through the substrate holder 201.Having been cooled, the polymeric substrate 203 is prevented from beingdeformed. Thus, heat treatment to crystallize the BiYIG thin film 207can be performed.

The BiYIG thin film 207 is crystallized by the above heat treatment,obtaining a large magneto-optical effect.

Further, since the polymeric substrate 203 is cooled as mentioned above,a thermoplastic resin substrate or a tape-shaped, film-shaped orsheet-shaped substrate can be used as the polymeric substrate 203,whereby easy handling of the substrate and downsizing can be realized.

In the above-mentioned conventional art, when an optical magneticrecording medium (magnetic optical member) is obtained using BiYIG, heattreatment at 600° C. or more is required to obtain excellent magneticoptical characteristics by crystallizing BiYIG. Thus, it is necessary touse glass as a substrate. On the other hand, in the present embodiment,the polymeric substrate 203 is cooled as mentioned above, and there isno need to use glass as a substrate. The guiding groove for laser lightis therefore easy to form, and since the substrate is not limited toglass (heat-resisting member), the member is applicable in wider field,whereby the improvement of the productivity can be attained.

Further, the (SiO₂/Ta₂O₅)^(n) layer 210 is cooled as described above,preventing the interdiffusion of Ta₂O₅ and SiO₂ in the (SiO₂Ta₂O₅)^(n)layer 210, so that the heat treatment for crystallization of the BiYIGthin film 207 can be performed. Further, by subjecting the BiYIG thinfilm 207 to heat treatment to crystallize, excellent magneticcharacteristics are generated, resulting in the production of the onedimensional magnetic optical crystal 200 (one dimensional photoniccrystal) having excellent magnetic optical characteristics. This onedimensional magnetic optical crystal 200 can be used as an opticalmagnetic recording medium, owing to the excellent magneticcharacteristics of the BiYIG thin film 207 obtained throughcrystallization.

Further, the one dimensional magnetic optical crystal 200 of(SiO₂/Ta₂O₅)^(n)/BiYIG/(Ta₂O₅/SiO₂)^(n) structure can find another usesuch as an optical isolator by separating the polymeric substrate 203joined thereto.

The first embodiment takes as an example a case where the polymericsubstrate 203 and the (SiO₂/Ta₂O₅)^(n) layer 210 are cooled through thesubstrate holder 201. However, the polymeric substrate 203 and(SiO₂/Ta₂O₅)^(n) layer 210 may be directly cooled.

During the heat treatment with the infrared ray introducing heater 220the thermocouple 223 is allowed to contact with the surface of theglassy carbon 204 to monitor the temperature. The heat treatment patternis shown in FIG. 3. Further, The X ray diffraction pattern and theFaraday rotational angle when the member is subjected to the heattreatment for crystallization by such heat treatment are shown in FIG. 4and FIG. 5, respectively. In the BiYIG thin film 207 that has anamorphous structure immediately after the film formation,crystallization thereof progresses at a heat treatment temperature of850° C., and the Faraday rotational angle shows the same value as in thecase where the film is heated and crystallized with a conventionalelectric furnace. Further, no surface roughening or a crack is found inthe BiYIG thin film 207 at all.

On the other hand, a substrate made of a thermoplastic resin such asPMMA (polymethyl methacrylate) and PC (polycarbonate) is heated by thesame heating process to perform a preliminary experiment. As a result,it has been found that no deformation or the like in the substrateoccurred, confirming that the above heat treatment does not brings aboutdeformation or the like to the polymeric substrate 203.

Further, heating treatment is performed on the multi-layer film havingthe (SiO₂/Ta₂O₅)^(n)/(Ta₂O₅/SiO₂)^(n) structure by the same heatingprocess, and transmissivity spectrum is measured on the multi-layer filmbefore heating and after heating. The results are shown in FIGS. 6A, 6Band FIGS. 7A, 7B. The design wavelength at this point is 750 nm and thethickness of each layer is {fraction (λ/4)} of the optical wavelength.

FIG. 6A shows a transmissivity spectrum before heat treatment, and FIG.6B shows the peak wavelength spectrum (partially enlarged transmissivityspectrum in FIG. 6A). FIG. 7A shows a transmissivity spectrum after heattreatment, and FIG. 7B shows the peak wavelength spectrum in FIG. 7A(partially enlarged transmissivity spectrum in FIG. 7A).

It can be seen from FIGS. 6A and 6B (before heating) that a photonicband gap appears in the wavelength region of λ=650 to 900 nm, and asharp peak appears at a position of λ=765 nm. Also seen from FIGS. 7Aand 7B (after heating) is that a photonic band gap appears in thewavelength region of λ=650 to 900 nm, and a sharp peak appears at aposition of λ=765 nm. Thus, as can be understood by comparing FIGS. 6A,6B with FIGS. 7A, 7B, the waveforms of the transmissivity spectrumsbefore heating and after heating are scarcely different from each other.This means that the cyclic structure of the multi-layer film having the(SiO₂/Ta₂O₅)^(n)/(Ta₂O₅/SiO₂)^(n) structure barely changes under a heattreatment condition which can crystallize the BiYIG thin film 207 byirradiation of the infrared beam using the infrared ray introducingheater 220.

Regarding the above-mentioned one dimensional magnetic optical crystal200 (one dimensional photonic crystal) with the(SiO₂/Ta₂O₅)^(n)/BiYIG/(Ta₂O₅/SiO₂)^(n) structure which is formed bysubjecting the (SiO₂/Ta₂O₅)^(n)/BiYIG to heat treatment and depositingthe (Ta₂O₅/SiO₂)^(n) film thereon, the transmitted wavelength spectrumand Faraday rotational angle are measured. The results are shown in FIG.8 and FIG. 9. As shown in FIG. 9, this one dimensional magnetic opticalcrystal 200 is found to have a large Faraday rotational angle.

In this embodiment since the infrared beam is adapted to beintermittently emitted (pulse heated), the crystallization of the BiYIGthin film 207 uniformly progresses to thereby obtain high accuracy.

Further, in this embodiment, the infrared beam is condensed with theglassy carbon 204 to rapidly carry out the heat treatment. Incidentally,this embodiment may be configured so that the heat treatment is carriedout without providing this glassy carbon 204.

The first embodiment takes as an example the case where the heattreatment for crystallization of the BiYIG thin film 207 is carried outusing infrared beam from the infrared ray introducing heater 220.However, the heat treatment for crystallization of the BiYIG thin film207 may be carried out using laser light from a laser heater 230(hereinafter referred to as a second embodiment) provided in place ofthe infrared ray introducing heater 220 as shown in FIG. 10.

In this second embodiment, a polymeric substrate 203 is set on asubstrate holder 201 with one surface of which the(SiO₂/Ta₂O₅)^(n)/BiYIG film is formed upward, and the(SiO₂/Ta₂O₅)^(n)/BiYIG is irradiated with laser light from a laser lightsource 231 while scanning the laser light in a wide range to crystallizethe BiYIG thin film 207.

Used in this case is the laser light having a wavelength with which thelight is not absorbed into the polymeric substrate 203 and the(SiO₂/Ta₂O₅)^(n) layer 210 (dielectric multi-layer film) but is absorbedinto the BiYIG thin film 207 (magnetic material film). For example, asshown in FIG. 11, laser light having a wavelength of λ_(a) or more withwhich the light is not absorbed into the polymeric substrate 203 and the(SiO₂/Ta₂O₅)^(n) layer 210 (dielectric multi-layer film) and thewavelength λ_(b) or less with which the light is absorbed into the BiYIGthin film 207 (magnetic material film), that is, laser light in awavelength range of (λ_(a) to λ_(b)) is used. Further, the laser lightis intermittently emitted (pulse-heated).

In this second embodiment, since the (SiO₂/Ta₂O₅)^(n)/BiYIG film isirradiated with the laser light having a wavelength with which the lightis not absorbed into the polymeric substrate 203 and the(SiO₂/Ta₂O₅)^(n) layer 210 (dielectric multi-layer film) but is absorbedinto the BiYIG thin film 207 (magnetic material film), the(SiO₂/Ta₂O₅)^(n) layer 210 (dielectric multi-layer film) is preventedfrom temperature rise also by the irradiation of the laser light, sothat interdiffusion of Ta₂O₅ and SiO₂ in (SiO₂/Ta₂O₅)^(n) layer 210 isprevented. On the other hand, only the BiYIG thin film 207 is heated bythe irradiation of the laser light and is crystallized.

In the heat treatment with the above-mentioned laser light, thepolymeric substrate 203 does not absorb the laser light and is preventedfrom temperature rise. Thus, as the polymeric substrate 203, athermoplastic resin substrate or a tape-shaped, film-shaped, or sheetshaped substrate can be used, realizing easy handling of the substrateand downsizing.

In the above-mentioned conventional art, when an optical magneticrecording medium(magnetic optical member) is obtained using BiYIG, heattreatment at 600° C. or more is required to obtain excellent magneticoptical characteristics by crystallizing BiYIG. Thus, it has beenrequired to use glass as a substrate. On the other hand, in the presentembodiment, the polymeric substrate 203 is prevented from temperaturerise as mentioned above, and it is not necessary to use the glass as asubstrate. Thus, the guiding groove for laser light is easy to form, andsince a substrate is not limited to glass (heat-resisting member), themember is applicable in wider field, whereby the improvement of theproductivity can be attained.

Further, since the (SiO₂/Ta₂O₅)^(n) layer 210 is prevented fromtemperature rise described above and the interdiffusion of Ta₂O₅ andSiO₂ in the (SiO₂/Ta₂O₅)^(n) layer 210 can be prevented, thecrystallizing heat treatment of the BiYIG thin film 207 can beperformed. Further, by subjecting the BiYIG thin film 207 to heattreatment to crystallize, excellent magnetic characteristics aregenerated and the one dimensional magnetic optical crystal 200 (onedimensional photonic crystal) having excellent magnetic opticalcharacteristics is produced. This one dimensional magnetic opticalcrystal 200 can be used as an optical magnetic recording medium, owingto excellent magnetic characteristics of the BiYIG thin film 207obtained through crystallization.

Further, in the second embodiment, since the laser light is adapted tobe intermittently emitted (pulse heated), crystallization of the BiYIGthin film 207 uniformly progresses to thereby obtain high accuracy.

Further, while scanning the laser light in a wide range, the(SiO₂/Ta₂O₅)^(n)/BiYIG is irradiated with the laser light. Accordingly,heating of the BiYIG thin film 207 can rapidly progress, wherebyimprovement of the productivity can be attained.

Further, in the second embodiment, the cooling mechanism 222 and thecooling treatment which are required in the first embodiment are notneeded. Therefore, the configuration of this embodiment becomes simplerand no cooling operation is needed, improving the productivity of theinvention.

The one dimensional magnetic optical crystal 200 (magnetic opticalmember) which can be obtained in the first and second embodiments hasthe large Faraday effect as mentioned above, and can exhibit excellentfunctions when used in various optical devices such as an opticalmagnetic recording medium (optical magnetic recording disk) and anoptical isolator.

The first and second embodiments take as an example a case where theBiYIG thin film 207 is used. However, the present invention is notlimited to this and can use other rare earth iron-garnet thin films.

According to the first aspect of the present invention, the magneticoptical member comprising a rare earth iron-garnet magnetic optical thinfilm and the crystalline magnetic optical thin film can exert excellentmagneto-optical effects.

According to the sixth aspect of the present invention, the rare earthiron-garnet magnetic optical thin film is crystallized by pulse heatingin which infrared beam is intermittently emitted without deforming thepolymeric substrate. Thus, when the polymeric substrate is formed with athermoplastic resin, or in a tape shape, a film shape or a sheet shape,it can be further easily handled as compared with the case where a glasssubstrate is used, and can be reduced in size.

Further, by cooling the polymeric substrate or preventing thetemperature rise of the substrate, deformation thereof is prevented.Thus, as the polymeric substrate, a thermoplastic resin substrate or atape-shaped, film-shaped, or sheet-shaped substrate can be used, wherebyeasy handling of the substrate and downsizing can be realized.Additionally, since a glass substrate is not required to use, theguiding groove for laser light is easy to form. The substrate is notlimited to glass (heat-resisting member), making the member applicablein wider field, and improving the productivity of the invention.

What is claimed is:
 1. A method of producing a magnetic optical membercomprising: two dielectric multi-layer films having a cyclic structurein which plural kinds of dielectric materials having different opticalcharacteristics are alternately laminated with regularity in thickness;a magnetic optical thin film of rare earth iron-garnet placed betweenone of two dielectric multi-layer films and the other of two dielectricmulti-layer films; and a polymeric substrate on which said magneticoptical thin film and two dielectric multi-layer films are formed;wherein: said magnetic optical thin film is laminated over saidpolymeric substrate with one of said two dielectric multi-layer filmsinterposed therebetween, while placing said polymeric substrate over awater-cooled substrate holder through an indium sheet; a glassy carbonis placed on a surface of said magnetic optical thin film; and saidglassy carbon is heated by pulse heating with intermittent irradiationby an infrared beam to crystallize said magnetic optical thin filmwithout deforming said polymeric substrate.
 2. A method of producing amagnetic optical member comprising: two dielectric multi-layer filmshaving a cyclic structure in which plural kinds of dielectric materialshaving different optical characteristics are alternately laminated withregularity in thickness; a magnetic optical thin film of rare earthiron-garnet placed between one of two dielectric multi-layer films andthe other of two dielectric multi-layer films; and a polymeric substrateon which said magnetic optical thin film and said two dielectricmulti-layer films are formed; wherein: said magnetic optical thin filmis laminated over said polymeric substrate with one of said twodielectric multi-layer films interposed therebetween, and said polymericsubstrate is directly cooled; a glassy carbon is placed on a surface ofsaid magnetic optical thin film; and said glassy carbon is heated bypulse heating with intermittent irradiation by an infrared beam tocrystallize said magnetic optical thin film without deforming saidpolymeric substrate.